JPH0734219A - Plasma ion nitrided stainless steel, its production and method of using it - Google Patents

Abstract

A process and apparatus is disclosed for the fabrication of press plates hardened by the use of plasma ion nitriding techniques to produce wear resistant decorative laminate containing alumina grit while improving associated press plate useful life. The application of this process to press plates having exacting final microfinish requirements is possible due to the determination of interdependancies between parameter settings and expected results. These interdependancies include the work piece geometry, surface and subsurface structure and desired results, process temperatures, pressures, and duration of heat-up time, thermal loading, reflective radiation and heat effects, cooling systems, and gas mixture composition.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a plasma ion nitride steel sheet used for applying pressure, and more specifically,
It relates to an improved and extremely durable plasma-nitrided stainless steel pressed sheet with a high quality microfinishing and a method of producing such a sheet used for producing wear-resistant decorative laminates.

[0002]

BACKGROUND OF THE INVENTION The manufacture of decorative laminates has undergone a series of innovations in the past, creating ever-increasing consumer expectations regarding the durability and resistance of the decorative laminate to scratches, scratches, rubs and scrapes. Is coming. Such wear resistant decorative laminates, especially high pressure resistant decorative laminates, have come to include the use of significantly harder grit of various sizes incorporated into the surface of the laminate. Although in the past some manufacturing methods have been utilized for some decorative laminates containing 6 micron grit such as 1 wt% in liquid resin and 15 micron grit such as 0.5 wt% in liquid resin, This product trend requires manufacturing processes with up to 30 micron grit such as 9 wt% in liquid resin to meet consumer wear resistance expectations of laminates.

The press plates used to produce decorative laminates are somewhat unique in their overall geometry. Press plates made from various grades of steel, especially stainless steel, are flat sheets of rectangular cross section, often with relatively large longitudinal and transverse dimensions, eg 4.88 and 1.525 m (16 and 5 ft, respectively). ). The press plate has such a large flat surface area, but its thickness is only about 3.
It is 175 mm (1/8 inch).

In the polished state, the press plate ideally has the appearance of a mirror-like sheet with a remarkably uniform flat surface or a fine finish with minimal microscopic discontinuities. In the case of a press plate that is actually polished, the quality of the fine finish of the press plate is determined by visually observing the reflection image on its surface and scrutinizing the reflection image to find optical differences. You can

Textured press plates made by mechanically shot peening, chemically etching, or a combination of the flat surfaces of pressed plates are usually polished plates. Much less glossy than, and although some defects are revealed by visual inspection,
Measuring the gloss with an instrument is usually the main way to specify its quality, rather than measuring the reflectance by visual inspection. Usually IS
The O or NEMA gloss unit meter gloss measurement method was established by the manufacturer of the laminate based on consumer expectations. The degree of gloss of the laminate is also directly related to the gloss of the press plate from which it is made. The greater the gloss of the press plate, the more obvious the press plate wear.

Also, as a large flat surface used to provide a surface finish to the cellulosic viscous resin matrix, the press plate should be as warp-free as possible. Such distortions generally take two forms. The first is a regular bend that occurs over the entire longitudinal or lateral dimension. To a moderate degree, such bends are usually 6.99 to 11.0.
It is acceptable as long as the pressed plate, such as in the range N / mm ² (1000 to 1600 psi), occupies a nearly perfect flat orientation under the pressing force of the press. The second type of strain occurs as localized strain and buckling with changes in the relative height of the press plate from a virtually perfect flat surface. Such a second type of distortion is
It is not corrected by the pressing force of the often press, thus causing the appearance of the often defective laminate and the disposal of the press plate. These two types of strain, caused by stress relief or uneven heating, often require effort to cure the press plate by conventional equipment.

[0007] Therefore, the level of manufacturing accuracy required to produce and maintain a distortion-free surface having an overall smooth fine finish on both sides of the press plate is extremely important. For example, press plates are usually used in the form of sandwiches with two composites of laminated resin impregnated paper placed in the middle, facing in opposite directions. So-called "pack"
Multilayer plates of alternating laminated materials and press plates called "packs" or "books" are loaded into the press and undergo consolidation by thermal curing and pressure treatment. If the press plate is excessively distorted in the first type or any of the second type and the surface microfinishing is imperfect, the finished decoration Significantly detrimental effects on the appearance of the automotive laminate are apparent.

However, the use of alumina grit to improve the wear resistance of decorative laminates produces conventional decorative laminates even with the small grit sizes and densities used in the past. It destroys the fine finish of the surface of the ordinary steel press plate used for.

The formation gr
It) and the physical interaction of the surface of the press plate with fine scratches and the resulting gloss, haze, noticeable spot wear of "weak" gloss and sometimes scraping of the metal. In addition, any surface microfinishing of the pressed board, such as when a fine finish of the surface of the pressed board gives the final laminate product its front surface finish, for example to give a decorative laminate a great gloss or textured surface finish. The flaws also render the press plates unusable and often require the damaged press plates to be remanufactured at a very high cost, or to be eventually disposed of for disposal.

Attempts to use pressed plates with even greater surface hardness have failed to obtain a technically and economically viable solution. A conventional polished stainless steel press plate, regardless of the size of the alumina grit used, produces severely unacceptable fine scratches after only one pressing operation. A textured stainless steel press plate also easily produces fine scratches due to alumina grit. Not as apparent by visual inspection, as is the highly polished plate for a much lower initial gloss and an inherently textured texture,
The gradual deterioration due to corrosion of gloss and texture caused by the use of large grit sizes and densities in part requires frequent refinishing.

If these stainless steel press plates are hardened by the usual heat treatment methods, the plates become too brittle, which can lead to stress fractures and strain becomes a significant problem. Chromium-plated steel pressing plates also suffer from severe micro-scratches after relatively few pressing operations. Chromium plating and post-baked electroless nickel deposition on stainless steel pressed plates have been utilized, but have not satisfactorily solved the problems of fine scratches and plate wear associated with grit. In addition, buffing and polishing operations on polished plates or refinishing operations by shot blasting used on textured plates tend to unevenly remove thinly plated layers, which is significant for re-plating surfaces. It costs money. The tendency to use larger size grit at higher density only exacerbates these problems.

Traditionally, iron-based alloys have been surface hardened by various treatments including deposition and diffusion of additional elements and compounds within the substrate, especially nitrogen and carbon. However, case hardening of stainless steel parts (case harden)
n) The wide variety of industrially practiced processes used to process may require dimensional limitations and high processing temperatures, often require subsequent oil or water quenching, unacceptable surfaces. Finished state and local strain (part)
There was a risk of causing a warpage). Therefore, these alternative methods are not practical for processing large, relatively thin press plates.

In the present invention, we have unexpectedly found that the concept known as plasma ion nitridation overcomes the disadvantages inherent in known press plate curing equipment, and it has been demonstrated that wear resistant laminates containing various densities of large alumina grit. It was the first to enable the production of pressed plates used in production.
Many applications of plasma ion nitriding technology have automated control and arc discharge suppression devices that adjust the input energy of the plasma to better control the quality of processing of significantly smaller articles or workpieces. MPT GmbH (Trademark) processing method (MPT GmbH Plas
The final fine finish, such as by ma-Triding process, has been applied to large articles with relatively small surface-to-volume ratios that are not an important decorative feature of the article. However, none of these applications have shown that plasma ion nitridation is a solution to the problem solved by the present invention.

Plasma ion nitriding is based on plasma discharge physics and operates by exposing the surface of a negatively charged metal workpiece to positively charged nitrogen ions. An electric potential is applied to this device in a vacuum state in the sealed container, the container becomes a positively charged anode (electron acceptor), and the work material is charged to a negatively charged cathode (cation acceptor). To form. High voltage energy strips electrons from the nitrogen-bearing gas molecules introduced into the anode to form a plasma, where the nitrogen ions are accelerated towards the workpiece. The collision of nitrogen ions with the surface of the material to be processed generates thermal energy by converting kinetic energy into potential energy. When nitrogen ions collide with the surface of the work piece, most of the ion atoms fly out at the collision point and combine with other nitrogen ions to form a glow discharge "joint" on the surface of the work piece. Forming iron nitride ions on the surface of the workpiece. These iron nitride ions then impinge upon and deposit on the heated workpiece surface and diffuse within the boundaries of the subsurface molecules, creating an exposed surface layer and a distinct subsurface structure that is not brittle. Greater hardness provides many desirable properties for the above-mentioned pressed plates, such as a flawless surface finish and a determined case hardening depth.

[0015]

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a hardened, flat work material such as a press plate for economically producing wear resistant decorative laminates. Is.

The main object of the present invention is to provide a plasma ion nitriding press plate which gives a significantly greater wear resistance life in the production of decorative laminates.

Yet another object of the present invention is to provide a press plate having a high quality fine finish with a long press plate life for economically producing wear resistant decorative laminates. Is.

It is also an object of the present invention to provide a press plate which is free from the disadvantageous distortions for economically producing wear resistant decorative laminates.

Another object of the present invention is to provide a method of producing a plasma ion nitriding press plate which provides a significantly greater wear resistance life when producing a decorative laminate.

Yet another object of the present invention is to provide process parameters for producing plasma ion nitriding press plates for economically producing wear resistant decorative laminates.

Yet another object of the present invention is to provide a method of using a pressed plate cured by a plasma ion nitriding process to economically produce a wear resistant decorative laminate.

Other objects, advantages and features of the invention will be in part apparent and in part explained with reference to the following detailed description and claims, and also with reference to the accompanying drawings.

[0023]

According to the present invention, a method and an apparatus for curing a press plate by utilizing a plasma ion nitriding technique has been developed, which was realized in the knowledge of the applicant of the present invention. Plasma ion nitriding of such large workpieces has never been attempted or successful.

The application of the plasma ion nitriding method to large workpieces with ultimate precision finishing requirements as described in the present invention has been demonstrated between parameter setting and expected results. Great progress because of the complex relationship. These relationships are the geometry of the work piece, the surface and subsurface texture of the material and the desired result, processing temperature, pressure and heating time, thermal loading, radiative and convective thermal energy effects, cooling. Includes system requirements and gas mixture composition.

Accordingly, testing and analysis are interrelated to allow for correct parameters, interrelationships of functional parameters and permissible variations within each functional parameter or group of functional parameters to produce a desired product specification. Is decided. For that purpose, a general geometric formula is determined which describes the surface-to-thickness ratio of the pressed plate for which the required parameters are applied.

[0026]

For a better understanding of the present invention, reference should be made to the drawings illustrating in detail the embodiments of the invention and to the following description illustrating the examples of the invention.

Referring to the drawings, where like numerals indicate similar or corresponding parts, FIG. 1 shows the overall shape of the reaction vessel 10 and stainless steel press plate fixture 100 as assembled. The reaction vessel 10 related to the present invention Terumiyon ® (THERMION ^TM) M page tape using a processing and control unit gate em based hard plasma - used by preparative Riding ®.

However, for the purpose of simplifying the description, the container 1
0 includes a cylindrical outer wall 12, a cylindrical inner wall 13, and a cylindrical heat deflection shield 14, all of which are concentrically arranged within the outer wall 12. Other vessel geometries (ie, horizontal rectangular chambers) and controller configurations can also produce the desired results, and the dimensions of the vessel are the dimensions placed on the press plate being processed. It should be understood that the only limitation is the receptor.
Outer wall 12, inner wall 13 and heat deflection shield 14 act as an anode during the nitriding process as described below. Between the outer wall 12 and the inner wall 13 is an annular cooling chamber 16 in which cooling water 18 is circulated to help maintain a critical process temperature as described below. ing. The outer wall 12, the inner wall 13 and the heat deflection shield 14 have a viewing port 20 to allow "glow inspection" of the press plate during the nitriding process. Inner wall 13
The heat deflection shield 14 is preferably formed of stainless steel or an alloy to prevent the outer metal from separating and contaminating the gas mixture treating the press plate.

The container 10 is further provided with a water supply device 22 to form an annular cooling chamber 16 having a continuous and regular supply of cooling water, which overshoots the press plate when the container is not inspected. To avoid excessive temperatures in the container 10 which may cause different temperatures and subsequently defective press plate distortion. The container 10 further includes a vacuum pump 24, a gas supply device 26 containing nitrogen,
A high voltage supply 28 and a control unit 30 are provided. The high voltage source 28 provides positively charged direct current to the container 10 and negatively charged direct current to the press plate fixture 100 contained therein. Control unit 3
Reference numeral 0 corresponds to the Telmyon (trademark) control device used in the above-mentioned MP Pete Gaem Behr Plasma-Triding (trademark) processing.

The fixture 100 shown in FIG. 1 comprises a base member 102, a support rod 104, a cross member 106 and a support arm 108. As shown in FIGS. 1, 2 and 3, the press plate 50 is suspended from the support arm 108 by the tightening device 110 and the suspension rod 112. The press plates 50 must be separated by a distance sufficient to avoid interaction between the glow discharge plasma boundary of one press plate and the boundary of an adjacent press plate. In addition, this distance should be such that heat transfer is avoided by minimizing the transfer of heat from one press plate to the adjacent press plate. In the first test, this distance was about 20.3 cm (8 in)
It has been shown that it is desirable to do this or more.
However, other press plate dimensions require different spacing ranges.

As better shown in FIGS. 2 and 3, the tightening device 110 is a simple clevis supported by a suspension rod 112. 1 notch on the opposite top
16 are formed, and the press plate 50 usually has a length of 3.18 m.
It is adapted to slidably accommodate a thickness portion made to m (1/8 inch). Press plate 50 is notched once 1
When inserted in 16, the tightening device 110 is fixed to the press plate 50 by the tightening device 118 for tightening. The tightening device 110 is then attached to the support arm 108 by the suspension rod 112. In order to reduce the amount of heat absorbing material around the edges of the press plate 50, the tightening device 110 provides a notch by machining or milling the protruding corners 120 (shown in phantom). Tapered inward toward 116. Therefore, it has been found that the amount of material that absorbs heat from the press plate 50 is minimized, which is an important feature of the present invention. In order to avoid distortion, it is important that the press plate 50 be exposed to the smallest possible temperature changes. Therefore, by clamping each press plate 50 to a clamping device 110 attached to a support arm 108 connected to a cross member 106, the press plates 50 are brought into substantial thermal interaction with the fixture 100 within the container. It will be possible to hang it without occurring.

The preferred method of nitriding is an MP coating that utilizes the above-mentioned Termim ™ processing and control system.
Game Behr Plasma-Triding (TM)
It depends on the processing. This method uses an electronic controller with an arc discharge suppression controller to minimize press plate defects. Special processing conditions have to be used for the pressed plates according to the invention,
This is explained below. If not controlled, the impact of nitride ions often results in heat energy and work piece temperature that destroys the usefulness of large work pieces such as press plates. Such obstacles include faulty distortions, buckling and arc traces ("cobweb marks").
And “blister”), localized melting (“comet's tail”), tightness “holes” and other defects caused by defective effects on the microfinishing, including imperfections such as assisting damage to the work piece. Is. Therefore, the commercial use of plasma nitriding for the hardening of large workpieces such as press plates with unusually large surface-to-volume ratios has heretofore not been considered feasible.

According to the invention, the treatment of the pressed plate to be treated begins with a two-step purification treatment of prenitriding to remove water-soluble, oil-soluble and insoluble resins from the work piece. These processes often cause "arc marks". Failure to remove any of these residues will result in a particularly strong arc discharge during the first nitriding process,
This may damage the fine finish of the press plate 50.

The residue on the surface of the press plate is usually the press plate 50.
This is because there is a minute amount generated by the treatment at an early stage. The freshly refinished abrasive press plate appears clean to the eye but retains any residual abrasive or buffing compound deposited on the surface (commercially available in rouge (r
called))). Such rouge is usually a waxy material (solid at room temperature but melts when applied to a heated press plate during processing)
Composed of very fine abrasive material such as alumina combined with or because the abrasive material is combined with a fatty acid "grease" in the form of a water-based emulsion (liquid at room temperature) is there. A newly re-finished textured press plate using shot peening technology is created by the destruction of the shots normally used in the blasting process, which causes the residue of very fine dust to adhere to the surface of the press plate by electrostatic charge. Have. Occurring on any type of press plate, fingerprints due to the oil and other external oil and grease spots, especially on textured press plates, are a common type of contamination. In addition, press plates, especially press plates that are not newly refinished, have a trace amount of release material (external release material) applied directly to the press plate, which is usually deposited on its surface, but most often the liquid surface resin itself. Has a release material (internal release material) incorporated therein. These release materials promote easy separation of the press plate from the laminate after it has been cured by the pressing operation. The most widely used release agents are fatty acid-based, ordinary oleoic acid soaps (stearate / palmitate mixture), zinc stearate powder (directly applied to the press plate). And various commercially available ones known to those skilled in the art.

This two step cleaning process involves first completely cleaning the plate with deionized water.
After it has been dried, the press plate is thoroughly washed with a chlorinated hydrocarbon solution, which is preferably a 1,1,1-trichloroethane solution. In this way, both the water-soluble and oil-soluble materials are dissolved and removed from the press plate with the remaining insoluble particles due to the physical cleaning action.

The press plate 50 is then attached to the fixture 100 as described above. As an important feature of the invention, the loading and fixing of this press plate has a direct effect on the choice of process parameters. The thermal loading of the press plate produces thermal energy by radiation and convection, which also requires the correct adjustment of the temperature of the press plate. Dissipation of the generated thermal energy is controlled by adjusting the input voltage, the flow velocity of the cooling water chamber 16 and the distance between the press plates 50 in the container 10.

The temperature sensing device, which is preferably a thermocouple 52 located within the loaded container 10 as shown in FIG. 1, is the primary element that regulates the thermal energy generated within the container 10. Is. It has been found that placing thermocouple 52 at the edge of a centrally located press plate attached to fixture 100 is an ideal placement for such a geometry. Due to plasma physics and due to ion bombardment of all "edges" or "corners" to the surface, the edges or corners heat up more quickly than the central part of the press plate 50. Therefore, the surface temperature of the outer peripheral portion of the plasma 50 rises a little faster than the central portion of the plate. Therefore, the thermocouple 5 at the edge
2 gives a better control effect on the heating rate and a more harmonious temperature condition through the cross section of the press plate 50. It has been found that placing the thermocouple in other locations will give erroneous temperature data, which tends to confuse the inputs of the controller 30, which can lead to distortion and uneven case hardening hardness. ing.

The container 10 is sealed after being loaded, and the air is evacuated by the vacuum pump 24 so that a vacuum is generated inside. The vessel 10 is then passed through a nitrogen gas supply 26 with a nitrogen-containing gas such as gaseous ammonia at 3 to 8 mbar (0.04 to 0.12 ps).
It is filled with pressure up to i). Other gaseous mixtures containing nitrogen atoms can also be used to advantage. For example, for press plates with high chromium content, a mixture of nitrogen and hydrogen is recommended. This is because hydrogen promotes the formation of chromium nitride. Moreover, the gaseous mixture can be more easily controlled for purity and dryness. However, in the case of substrates with low or no chromium content, excessive hydrogen concentrations can lead to hydrogen embrittlement. The use of a carbon-containing gas such as methane in a gas mixture is a carburizing process.
It is not recommended because of the harmful effects of n).

Next, a voltage is applied to this apparatus by a high voltage supply source 28, and a glow discharge is formed around the press plate when the process proceeds to the sputtering process. The arc discharge generated in the glow discharge is directed toward the residual residue and deposited on the work material, and serves as the final purification treatment. In this way, the residue or deposit is evaporated and removed from the work piece. At this time, the work material itself is only about 93.33 ° C (200 ° C).
It only slowly increases to the temperature of F). This condition, which corresponds to area I in FIG. 4, continues until all deposits have been removed and the arc is extinguished.

The voltage is then constantly increased as shown in range II of FIG. 4 to accelerate the ion bombardment and initiate a temperature increase to the best temperature for the nitriding process. During this condition, the unaided human eye is used to perform "glow inspection" operations. Since this operation requires adjustment of the rate of increase of the power input, a "glow inspection" is performed through port 20 of vessel 10 to observe the uniformity and color of the glow discharge. Press plate 5
When 0 starts glowing around its outer peripheral surface, the central part of the press plate 50 is brought to the same temperature without causing a great imbalance in the potential damaging temperature between the edge part and the central part of the press plate 50. It is important to do so. Therefore,
When the outer peripheral edge of the press plate 50 glows and shows an appropriate temperature as can be seen by the correct glow emission color,
The voltage value is held for about 1 hour, as indicated by the range III in FIG. 4, so that the rest of the press plate reaches a uniform temperature distribution. This glow emission temperature should be kept at about 70 to 80% of the maximum nitriding temperature.

The press plate 50 must also be inspected for "hot spots" during this period. Since the color of the glow emission is directly proportional to the surface temperature of the press plate, any change in color indicates a change in temperature and such a change in temperature must be avoided. As mentioned above, the temperature can be controlled by the voltage input and the flow rate of water through the cooling chamber 16.

Once the temperature of the work material is stabilized,
The voltage is increased to 100% of the voltage required to obtain the maximum desired temperature as shown in range IV of FIG. 4 and the automatic processor controls the rest of the process as shown in range V of FIG. Make it possible. During the cooling process shown at VI in FIG. 4, the controller 30 is also used for a period of time during which the container 10 is held under vacuum to avoid oxidation of the press plate 50. The flow of water in the cooling chamber 16 must also be maintained.

During the range I, II, III, IV and V, an additional nitrogen-containing gas is admitted into the vessel 10 and ionized and consumed by the gas or vacuum system deposited on the workpiece. Gas must be replenished.
In this way, additional gas must always be introduced at a very slow flow rate to maintain the partial pressure of the vessel. Such flow rates are determined in relation to cycle time and modified as needed.

Based on the results of the experimental tests, the process parameters found to be most advantageous for the geometry of the pressed plate are shown in Table A.

[0045]

[Table 1] Table A Parameter settings Range in Figure 4 Maximum temperature 400-450 ℃ (750-850 ° F) Pressure 3.0-8.0mb (0.04-0.12 psi) Heating time 12-20 hours Range I and II Treatment time 20- 48 hours Range III, IV and V Cooling time 2-8 hours Range VI

The selection of the parameter "set value" is related to the desired hardness and case hardening depth of the workpiece. This hardness is evident in two parts of the work piece, the compound layer and the diffusion layer. A compound layer is formed on the exposed surface and consists essentially of some percentage of the chromium nitride compound in the case of iron nitride compounds and stainless steel. The diffusion region found under the compound layer is hardened to a slight extent due to the decrease in the concentration of the nitride compound caused by the propagation of nitrogen ions and iron ions within the grain boundaries. The hardened compound layer and diffusion layer areas that define the thus hardened case hardening depth are now related to the material and geometry of the press plate 50. It should be noted that voltage (and corresponding temperature) and processing time are inversely related. If the processing time in range V is extended, the overall maximum temperature is reduced.

The geometrical formula developed in connection with the present invention considers the ratio of surface area to thickness. 2.54c
0.093 m ² (1f for m (1 in) plate thickness
The surface area relationship of t ² ) is 5.5 m ² / cm to 10
2.5m ² / cm (150ft ² / in to 2800f
It must be up to t ² / in). These values are for a press plate having a nominal dimension of 0.9 m x 2.1 m (3 ft x 7 ft) with a thickness of 0.64 cm (1/4 in) and a thickness of 0.16 cm (1/16 in). With 1.5m x 4.9m (5ft x 16ft)
Corresponding to each press plate having the nominal dimensions of. Combinations of length, width and thickness within these numerical ratios are within the indicated parameters of the invention.

The desired compound layer depth is 0.0025 to 0.0102 mm (0.0001 to 0.0004i).
It has been determined up to n). The overall desired case hardening depth, including the compound and diffusion layers, is 0.025 to 0.102 mm (0.001 to 0.02 mm).
It is up to 04 in). However, the thickness of other compound layers and diffusion layers can also be obtained in relation to the special requirements of the final product.

After reaching the room temperature, the container 10 is opened,
The press plate 50 is preferably removed from the unsealed container 10. However, the temperature of the press plate 50 is about 1
It can also be removed when cooled to 200 ° F (00 ° C). Although removing it before the plate 50 reaches room temperature for the purpose of improving productivity shortens the processing time by 6 hours, this also means that when the container 10 is opened it is exposed to the hot plate 50. This causes some oxidation of the surface of the pressed plate caused by room temperature air. This layer can be scraped if desired. If the workpiece is allowed to reach room temperature, ie, a significantly longer cooling time, as opposed to the short 2-8 hour period described above, less oxidation and a brighter finish can be obtained. It has been found that Oxidation caused by room temperature air flowing into the container 10 while the press plate 50 is at room temperature or higher introduces nitrogen or an inert gas into the container without applying a voltage to accelerate the final stage of the cooling process. Can be avoided by

It is emphasized, however, that promoting the cooling rate when the plate is still at elevated temperatures (between processing temperature and about 200 ° F.) results in a solution of plate stress with deformation. That is what must be done. The colder air flowing into the container 10 is uniformly pressed by the press plate 5
Instead of contacting zero, a steep thermal gradient is created, which involves the solution of stress. The temperature of the cooling chamber 16 is reduced, the flow rate of the cooling chamber 16 is increased, allowing the container 10 to flow to the atmosphere (which also causes some oxidation of the surface of the press plate), or the inert " The introduction of "cooling gas" is the mechanism by which all elevated temperatures enable the release and deformation of such stresses. The higher the temperature intended to provide such accelerated cooling, the more pronounced the deformation of the press plate and the possible oxidation.

To recognize the benefits of the present invention, "usually" used to make grit-free decorative laminates.
It is pointed out that the uncured, abraded press plate must be refinished approximately every 200 cycles of operation due to damage during normal processing. More critical, such as dark or black uniform color laminates
The board used to press the ical) color laminate should be re-used after as few cycles as possible, such as 30 to 50 cycles, to prevent damage during processing to maintain acceptable laminate finish quality. It must be finished or else it will result in a loss of quality.

In addition to the evaluation of the optical distortion used to determine the surface finish quality of the pressed plate, the surface finish quality of the laminate produced by the pressed plate is determined by the surface finish quality of the pressed plate. Can be used to make decisions. NEM
The A60 degree gloss measurement is commonly used to characterize the finish of laminates. In recent years, as the market has become more and more demanding, there has been a demand for a high gloss surface without clouding. Thus, the scale shown in Table B is generally accepted in the field of industry.

[0053]

[Table 2] Table B Gloss finish quality of laminated sheet ≧ 100 Excellent 95-99 Good-very good 90-94 Marginal <90 Unacceptable

In order to measure the performance improvement with the nitrided press plate, the most severe test of press plate finish quality against a black gloss finish "trial" laminate was performed on a full surface 1.22 as shown in Table C. × 3.05m (4ft × 10f
It was carried out using the polished press plate of t). The grit used was aluminum oxide incorporated in a liquid melamine surface resin.

[0055]

[Table 3] Table C Number of press operations that produce commercially unacceptable fine scratches Surface grit Standard Hard chromium Plasma Ion size / load 410 SS plating 410 SS Nitriding 410 SS 5% 3μ 1> 81 ^* NA 1% 6μ 1 8 234 1% 6μ and 1 NA> 100 ^{** and} 0.5% 15μ 0.8% 6μ 1 1 NA and 1.6% 25 μ 9% 30u μ 1 NA> 15 <33 ^* 8 times press NEMA 60 degree gloss 99.1 ^** One press NEMA 60 degree gloss 98.5 with Dorigon gloss 43.5 and haze index 1.2.
0 NEMA 60 degree gloss 97.1 at 100 presses, Dorigo gloss 60.7 and haze index 0.93

For example, a laminate produced with 3μ grit as a liquid resin 5% by weight in a test using a chrome polished plate showed that the deterioration of the fine finish of the plate and of the laminate was caused by fine scratches. It was. It should be noted that the NEMA gloss value for this test was very good at 99.1, dropping from a level of almost excellence to a marginally acceptable level of only 95.8, 55
It was shown that significant plate wear occurred during the period of one press work. Additional press work up to at least 81 times continued to tend to be less acceptable.

On the contrary, 6 μ and 15 which have a much stronger action force
100 by nitriding polishing press plate using μ grit
After a number of pressing operations, the gloss remained constant in the good to very good range. Since Dorigo gloss is a very good indicator of the finish quality of glossy laminates, it is an important indicator of the quality of the abrasive plates from which the laminates are made. Experience has shown that a Dorigon gloss of 40 or greater and a haze index of 1.5 or less are indicative of a fine finish of laminates and pressed plates of exceptional quality and significantly better reflectivity. It should be noted that even with such a relatively strong acting grease, the laminated plate produced after 100 pressing operations did not show any deterioration in Dorigo gloss.
Surprisingly, a very significant improvement in reflectance was obtained to a level rarely achieved by any polished plate. The nitrided press plate exposed to 1 wt% 6 micron grit in liquid resin was re-buffed after 234 cycles of operation and at least 103 other cycles of operation resulted in acceptable laminate quality. It has to be noticed that. Also, although the 9 wt% 30 micron grit in the liquid resin provided slightly limited press plate durability as compared to the smaller grit density and size,
Nevertheless, relatively frequent refinishing of the plate is allowed (roughly as often as a normal dark plate of "dark" color quality).
In some cases, it is possible to use a grit having a strong acting force.

It was also observed during these tests that the nitrided plates were more easily released from the laminate after the curing and pressing steps than the conventional polished pressed plates. . As stated above, the press plate is used with a composite of resin-impregnated laminated paper placed in the middle so that it faces in the opposite direction as shown in FIG. It consists of a press plate 50, a laminated material 200, a separating sheet 201 and a multilayer body of cushions 203 arranged on a support tray or “bread” 207 so as to form a “packing body” 202, these being the press 20.
4 is loaded between heating / cooling platens 205 for heating and pressure treatment to effect consolidation and curing. Heating / cooling platen 205 in press 204
The gap for moving the material between the two is limited by the opening or "daylight" 206 of the press, ie the space between the two platens when the press 204 is fully opened. It should be noted that it is clear from FIG. 5 that excessive plate distortion of this type can interfere with the ability to move the package 202 into the press 204.

Usually from 125 to 150 ° C. (260 to 30
After a curing time of about 45 to 90 minutes at a temperature of up to 0 ° F.) and subsequent cooling, the operator of the press in order to disassemble the package 202 into the press plate and the component parts of the finished laminate. A variety of changing physical efforts are required. For example, the ability to release textured boards is generally less than the ability to solve polished boards. Furthermore, any "residue" or small deposits of resin and fibrous material remaining on the press plate 50 will
It can be caused by transfer to the press plate 50 and subsequent contamination of the surface of the pressed laminate in the same press plate 50. In the worst case, the entire laminate can be physically bonded to the press plate 50, creating severe refinishing problems.

These problems are often reduced by using a release material that is often incorporated into the resin on the surface of the press plate, or by using a chrome plated plate. Surprisingly, it was found during the aforementioned press plate testing that the nitrided and hardened press plate was released much more easily than the normally ground steel plate. Deposits of the compound layer fill (seal) within the surface microstructure, and produce a smoother microfinish than is otherwise possible and adhere to the surface of the laminate in contact with it. It was theorized to reduce the tendency. Therefore, if the desired amount of release material is inadvertently omitted, or the above-described chrome plating difficulties must be avoided, then the use of a plasma ion nitride press plate can provide additional release capability. Expected.

Further, the invention described herein is a high pressure decoration.
Laminated plate (high pressure decora)
It is not limited to live laminate)
A large number of phenol resin-impregnated cells for high-pressure decorative laminates
Low score sheet (printed or uniform color sheet
Surface treatment by (solid color sheet)
Particles (other than cured and optional overlay)
Board or medium dense
Low-voltage decorative laminates such as fiberboard base layers
(Low pressure decorative
can also be applied to advantage)
Is. 6.9 to 11.0 for high voltage decorative laminates
N / mm²Range (1000 to 1600 psi)
Low pressure decoration for about 45 to 90 minutes curing period at pressure
For laminated board is 1.4 to 2.1 N / mm ²(200 to 3
Cycle time of about 1 minute at pressures up to 00 psi)
To do. Quick used to manufacture low voltage decorative laminates
Grit with strong action in the laminate at different cycle speeds
Or using other hard materials such as
In terms of application, it rapidly deteriorates the press plate.
Thus, the utility of the present invention is broadly applicable to decorative laminate products.
It can be applied to enclosures.

In the press test of Table C, a hardness of 65 HRc or more is desirable, but the hardness of the obtained plate is 38-45 HRc.
Was found to increase from 60 to 70 + HRc 4
Although limited to 10 stainless steel nitrided and polished plates, the potential applications for nitrided and hardened pressed plates are as broad as the grades of stainless steel that can be processed in this way are. Of. The use of a plasma ion nitriding textured press plate is associated with grit-related fine scratches compared to a normal textured steel plate,
It is expected to exhibit even greater durability in terms of wear and deterioration of gloss.

Moreover, while 410 stainless steel is historically the material of choice, press plates of 630 and 304 alloy stainless steel also have advantages.

630 stainless steel is similar to 410 stainless steel, but has about half the carbon content (0.05-0.08% vs. 0.
15%), a special precipitation hardening method (precipita)
It has the same hardness (42-45HRc) according to the ion hardening process. A low carbon content is desirable for etching textured plates. Full size (1.22 x 3.05 mm
Tests with (4 ft x 10 ft) textured plates according to the invention show a case hardening hardness of 42-45 HRc to 67-70.
It was increased to HRc.

Testing of limited 304 stainless steel was also performed according to the present invention. 304 stainless steel 4
Larger chromium content (18.0-compared to 10 stainless steel)
20.0 vs 11.5-13.5) and nickel content (8.0-10.5 vs 0.75) (annealed "bulk unhardened").
e) Austenitic steel. 304 stainless steel plates, including high-gloss mirror-finished plates, are sold commercially and are used as press plates due to their low price, but these plates also due to their softness, have scratches and other defects. The plate is easily damaged by handling. 304 stainless steel is so soft that it is recorded on the Rockwell C hardness scale (the "softer" Brinell scale scratch hardness is 140 for 304 alloy and 390 for 410 alloy).
The case hardening obtained after utilizing the present invention was 73 HRc compared to only 29 HRc at the beginning. Thus, the plasma ion nitriding of 304 stainless steel is expected to greatly solve the conventional problems of 304 stainless steel. Another alternative application is also present, namely chromium nitride rock plate, which is applied to further increase hardness.

Detailed structures, materials and arrangements of various parts of particular embodiments have been described and illustrated to illustrate features of the invention. However, it will be apparent to those skilled in the art that various modifications can be made without departing from the invention, which is limited to the claims.

[0067]

Since the present invention is constructed as described above, it has a hardened, flat, long life and high quality for economically producing wear resistant decorative laminates. There is provided a plasma ion nitriding press plate having the above fine finish and a manufacturing method thereof.

[Brief description of drawings]

FIG. 1 is a simplified perspective view of a nitriding container associated with the present invention that incorporates a press plate fixture.

FIG. 2 is a front elevational view of the tightening device for the press plate fixing tool taken along the line of sight 2-2 shown in FIG.

3 is an elevation view of the tightening device of the press plate fixing tool taken along the line 3-3 shown in FIG.

FIG. 4 is a diagram showing a temperature curve over time of the method according to the invention.

FIG. 5 is an elevation view of a representative press and package using a press plate according to the present invention.

[Explanation of symbols]

 10 Reaction Vessel 12 Outer Wall of Reaction Vessel 10 13 Inner Wall of Reaction Vessel 10 14 Heat Deflection Shield of Reaction Vessel 10 16 Cooling Chamber 18 Cooling Water 20 Visual Port 22 Water Supply Device 24 Vacuum Pump 26 Gas Supply Device Containing Nitrogen 28 High Voltage Supply Source 30 Control Unit 50 Press Plate 100 Press Plate Fixture 102 Base Member of Press Plate Fixture 100 104 Support Rod of Press Plate Fixture 100 106 Cross Member of Press Plate Fixture 100 108 Support Arm of Press Plate Fixture 100 110 Tightening Device 112 Suspended rod 120 Excised corner of tightening device 110 Laminated material 201 Separation sheet 202 Packaging body 203 Cushion 204 Press 205 Heating / cooling platen 206 Press opening or gap 207 Support tray or pan

Claims (12)

[Claims] 1. An iron-based press plate for producing a decorative laminate, a flat surface that substantially forms the surface finish of the decorative laminate, and a nitriding to a hardness of at least 55 HRc, at least 0. An iron-based press plate comprising: a hardened case hardening having a total case hardening depth of 00254 mm (0.0001 in). 2. The iron-based press plate of claim 1, wherein the press plate has a mirror-like surface finish that is substantially free of optically identifiable surface defects and distortions. 3. The press plate is a stainless steel rectangular prism having a first side dimension of at least 0.915 m (3 ft) and a second side dimension of at least 2.135 m (7 ft).
2. The iron-based press plate of claim 1, wherein the iron-based press plate is adapted to have a third side dimension of less than or equal to 6.35 mm (quarter inch) or less. 4. The press plate comprises 49.37 m ² / cm vs. 921.57 m ² / cm (150 ft ² / in vs 280).
The iron-based pressed plate according to claim 1, wherein the iron-based pressed plate has a surface area with respect to the thickness of the plate at a dimensional ratio of 0 ft ² / in). 5. The press plate is made of an iron-based material and is adapted to receive nitrogen ion bombardment generated by glow discharge, the glow discharge containing nitrogen from a gas or gas mixture containing nitrogen atoms. Assisting the deposition of ions on and in the surface of the press plate to increase its hardness and raise the temperature of the press plate to a temperature substantially below 537.78 ° C (1000 ° F). The iron-based press plate according to claim 1, wherein 6. The iron-based press plate according to claim 5, wherein the gas is a mixture of nitrogen and hydrogen. 7. The iron-based press plate according to claim 5, wherein the gas is ammonia. 8. An apparatus for producing a decorative laminate sheet, the apparatus supporting a mixture of resins and a base material as a substantially flat layer, and substantially forming a surface finish of the decorative laminate. Having a flat surface and having a hardened case hardened by nitriding to a hardness of at least 55 HRc, the case hardened part being at least 0.00254 mm (0.0001 in)
An iron-based plate adapted to have a full case hardening depth, and a device for pressing the flat plate against the resin mixture and substrate material to form a generally flat laminate. An apparatus for manufacturing a decorative laminated sheet containing a. 9. The laminate is formed by the resin mixture containing 1 wt% 6 micron alumina grit liquid resin, the laminate having a NEMA 60 ° gloss of 95 or more after 200 presses with the press plate. An apparatus for manufacturing the decorative laminated sheet according to claim 8, which is configured to include: 10. The laminate is formed of a resin mixture containing 1 wt% 6 micron alumina grit liquid resin and 0.5 wt% 15 micron alumina grit liquid resin, wherein the laminate is pressed 100 times with the press plate. An apparatus for producing a decorative laminated sheet according to claim 8, which has a gloss of NEMA 60 ° of 95 or more after being pressed. 11. A method of making an iron-based press plate for making a decorative laminate, wherein the press plate comprises a flat surface that substantially forms a surface finish of the decorative laminate. In the above method, an iron-based press plate is manufactured, the press plate is washed to remove residues, the press plate is suspended in a container capable of nitriding an iron material, and the press plate is Is heated by a glow discharge to assist the deposition action of nitrogen ions on and inside the press plate from a gas or gas mixture containing nitrogen atoms to increase its hardness and substantially increase the temperature of the press plate. 537.7
Raised to a temperature of 8 ° C. (1000 ° F.) or less, and press the press plate at least 2 times with the gas containing nitrogen atoms.
By exposing for a long time of 0 hours and exposing to nitrogen ion bombardment generated by glow discharge, a total case hardening depth of at least 0.00254 mm (0.0001 in) with a hardness of at least 55 HRc. A method for producing an iron-based plate, which comprises the steps of producing a hardened case hardened part having the above, cooling the press plate, and removing the press plate from the container. 12. The heating step is interrupted to stop the heating at about 93.33.
Glow discharge of the press plate is visually inspected during a temperature rise of 200 ° C. (200 ° F.) or more, and the heating process is interrupted within a range of 70 to 80% of the maximum temperature to make the press plate uniform 12. The method further comprises various steps for enabling a uniform temperature distribution.
A method for producing an iron-based plate as described in 1.